This invention concerns a method of and an apparatus for burning waste gases containing gaseous silane or silane gas for use in the processing of such exhaust gases and, more specifically, it relates to a method of and an apparatus for burning exhaust gases containing gaseous silane wherein a barrier of an inert gas atmosphere is formed near the top end of an injection nozzle introduced to the inside of a combustion chamber, so that spontaneously flammable gases contained in the exhaust gases are burnt ahead of the inert gas atmosphere.
Exhaust gases containing a silane gas discharged from the reactor of a semiconductor manufacturing plant or the like are highly toxic and tend to ignite spontaneously upon contact with air. In one of the methods for processing exhaust gases of this type, the exhaust gases are diluted with nitrogen gas and then washed and decomposed in a scrubber, followed by discharging. However, this method involves various drawbacks in that the toxicity and the flammability of the gases can not completely be eliminated due to the insufficient decomposition of the gaseous silane in the exhaust gases or in that the decomposition products are accumulated within the scrubber.
In an alternative method, in view of the above, the exhaust gases are fed as they are to a combustion equipment, where the gaseous silane in the exhaust gases are oxidized and decomposed through the combustion reaction with air in the combustion equipment and, then, they are washed in the scrubber. In this method, however, when the gaseous silane contained in the exhaust gases discharged from an exhaust gas nozzle are brought into the combustion reaction with the air in the combustion equipment, oxides, particularly, silicon oxides are formed through the combustion and deposited at the top of the nozzle and gradually grow thereon to narrow the inside of the nozzle. This hinders the complete burning of the gaseous silane and, as the result, the exhaust gases are discharged as they are while possessing the toxicity and the flammability. Furthermore, if the silicon oxides deposited on the top end of the nozzle further grow, the bore of the nozzle is clogged, thereby causing the pressure increase within the exhaust gas pipe. Then, when the pressure inside the pipe reaches a certain high level, the mass of the silicon oxides blocking the inside of the nozzle is scraped off by the pressure, and the exhaust gases are rapidly discharged in a great volume, which results in the extremely dangerous explosive burning in the combustion chamber.
In addition, since the mass of the silicon oxides thus formed is relatively large, it gradually deposits within the combustion chamber and requires much labour for the maintenance of the combustion equipment.